From: Masahiro Yamada > Sent: 01 March 2022 09:06 > > On Tue, Mar 1, 2022 at 11:28 AM David Laight <David.Laight@xxxxxxxxxx> wrote: > > > > The return value from fprintf() is normally the number of bytes written to > > the internal buffer (8k in glibc?) > > > > Only if the buffer is full and an actual write() is done do you get any indication of an error. > > > > So you can use the error return from fprintf() to terminate a loop – but it usually > > just isn’t worth the effort. > > > > The error status returned by ferror() is ‘sticky’, so you need only check once. > > > > But you need to check before fclose(). > > > > Since fclose() has to write out the buffer – that write can also fail. > > > > I’m not sure whether fclose() returns and error in that case, but adding fflush() > > makes the coding easier. > > > I just checked this. > > fclose() returns -1 if it fails to flush the buffer. But you still need to check ferror() before it. So you might as well do fflush(); if (ferror()); fclose(); Then there is only one error exit path. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
